U.S. patent application number 16/899044 was filed with the patent office on 2021-01-07 for multi-charged particle beam image acquisition apparatus and multi-charged particle beam image acquisition method.
This patent application is currently assigned to NuFlare Technology, Inc.. The applicant listed for this patent is NuFlare Technology, Inc.. Invention is credited to Kazuhiro NAKASHIMA.
Application Number | 20210005422 16/899044 |
Document ID | / |
Family ID | |
Filed Date | 2021-01-07 |
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United States Patent
Application |
20210005422 |
Kind Code |
A1 |
NAKASHIMA; Kazuhiro |
January 7, 2021 |
MULTI-CHARGED PARTICLE BEAM IMAGE ACQUISITION APPARATUS AND
MULTI-CHARGED PARTICLE BEAM IMAGE ACQUISITION METHOD
Abstract
A multi-charged particle beam image acquisition apparatus
includes an image acquisition mechanism, including a stage on which
a target object is capable to be disposed and a deflector for
deflecting multiple charged particle beams in array arrangement,
configured to acquire, in a state where a scan region width to be
scanned by each of the multiple beams has been set depending on an
image averaging frequency, image data of each beam by scanning the
target object with deflected multiple beams while relatively
shifting a stage moving direction angle and an array arranging
direction angle of the multiple beams from each other, and an
averaging circuit configured to average, using image data of each
beam, errors of the image data by superimposing image data of the
same position at the image averaging frequency.
Inventors: |
NAKASHIMA; Kazuhiro;
(Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NuFlare Technology, Inc. |
Yokohama-shi |
|
JP |
|
|
Assignee: |
NuFlare Technology, Inc.
Yokohama-shi
JP
|
Appl. No.: |
16/899044 |
Filed: |
June 11, 2020 |
Current U.S.
Class: |
1/1 |
International
Class: |
H01J 37/317 20060101
H01J037/317; H01J 37/22 20060101 H01J037/22; H01J 37/147 20060101
H01J037/147 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2019 |
JP |
2019-123994 |
Claims
1. A multi-charged particle beam image acquisition apparatus
comprising: an image acquisition mechanism, including a stage on
which a target object is capable to be disposed and a deflector
which deflects multiple charged particle beams in an array
arrangement, configured to acquire, in a state where a scan region
width to be scanned by each beam of the multiple charged particle
beams has been set depending on an image averaging frequency, image
data of the each beam by scanning the target object with the
multiple charged particle beams deflected by the deflector while
relatively shifting an angle of a moving direction of the stage and
an angle of an array arranging direction of the multiple charged
particle beams from each other; and an averaging circuit configured
to average, using the image data of the each beam, errors of the
image data by superimposing image data of a same position at the
image averaging frequency.
2. The apparatus according to claim 1 further comprising: an
individual region setting circuit configured to set an individual
scan region of the each beam on the target object which extends in
parallel to the moving direction of the stage, by relatively
shifting the angle of the moving direction of the stage and the
angle of the array arranging direction of the multiple charged
particle beams from each other, wherein the scan region width of
the each beam is set such that the individual scan region of other
beam is included in a direction perpendicular to the moving
direction of the stage.
3. The apparatus according to claim 1, wherein the image averaging
frequency can be set variably.
4. The apparatus according to claim 1, wherein the image averaging
frequency is set from two to a number of beams of the multiple
charged particle beams.
5. The apparatus according to claim 1, wherein, an individual block
region, being a quadrangle, whose side has a length of a beam pitch
indicating a pitch between mutually adjacent beams is set for the
each beam of the multiple charged particle beams, and the scan
region width of the each beam is set such that the individual block
region of other beam is included in a two-dimensional
direction.
6. A multi-charged particle beam image acquisition method
comprising: acquiring, in a state where a scan region width to be
scanned by each beam of multiple charged particle beams in an array
arrangement has been set depending on an image averaging frequency,
image data of the each beam by scanning a target object disposed on
a stage with the multiple charged particle beams deflected by a
deflector while relatively shifting an angle of a moving direction
of the stage and an angle of an array arranging direction of the
multiple charged particle beams from each other; and averaging,
using the image data of the each beam, errors of the image data by
superimposing image data of a same position at the image averaging
frequency.
7. The method according to claim 6 further comprising: setting an
individual scan region of the each beam on the target object which
extends in parallel to the moving direction of the stage, by
relatively shifting the angle of the moving direction of the stage
and the angle of the array arranging direction of the multiple
charged particle beams from each other, wherein the scan region
width of the each beam is set such that the individual scan region
of other beam is included in a direction perpendicular to the
moving direction of the stage.
8. The method according to claim 6, wherein the image averaging
frequency can be set variably.
9. The method according to claim 6, wherein the image averaging
frequency is set from two to a number of beams of the multiple
charged particle beams.
10. The method according to claim 6, wherein, an individual block
region, being a quadrangle, whose side has a length of a beam pitch
indicating a pitch between mutually adjacent beams is set for the
each beam of the multiple charged particle beams, and the scan
region width of the each beam is set such that the individual block
region of other beam is included in a two-dimensional
direction.
11. The apparatus according to claim 1, wherein the image
acquisition mechanism scans the target object with the multiple
charged particle beams deflected by the deflector while relatively
shifting the angle of the moving direction of the stage and the
angle of the array arranging direction of the multiple charged
particle beams from each other so that a plurality of beams of the
multiple charged particle beams are not arranged in parallel to the
moving direction of the stage.
12. The apparatus according to claim 1, wherein the image
acquisition mechanism acquires, in the state where the scan region
width to be scanned by the each beam of the multiple charged
particle beams has been variably set correspondingly depending on
the image averaging frequency having been set, the image data of
the each beam.
13. The method according to claim 6, wherein the target object is
scanned with the multiple charged particle beams deflected by the
deflector while relatively shifting the angle of the moving
direction of the stage and the angle of the array arranging
direction of the multiple charged particle beams from each other so
that a plurality of beams of the multiple charged particle beams
are not arranged in parallel to the moving direction of the
stage.
14. The method according to claim 6, wherein the image data of the
each beam is acquired in the state where the scan region width to
be scanned by the each beam of the multiple charged particle beams
has been variably set correspondingly depending on the image
averaging frequency having been set.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2019-123994
filed on Jul. 2, 2019 in Japan, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] Embodiments of the present invention relate to a
multi-charged particle beam image acquisition apparatus and a
multi-charged particle beam image acquisition method. For example,
embodiments of the present invention relate to a method for
acquiring a secondary electron image of a pattern which is emitted
due to irradiation by electron multiple beams and is to be imaged
by an inspection apparatus.
[0003] In recent years, with the advance of high integration and
large capacity of LSI (Large Scale Integrated circuits), the line
width (critical dimension) required for circuits of semiconductor
elements is becoming progressively narrower. Since LSI
manufacturing requires a tremendous amount of manufacturing cost,
it is crucially essential to improve its yield. However, as
typified by a 1-gigabit DRAM (Dynamic Random Access Memory), the
scale of patterns configuring an LSI is in transition from on the
order of sub-microns to on the order of nanometers. Also, in recent
years, with miniaturization of dimensions of LSI patterns formed on
a semiconductor wafer, dimensions to be detected as a pattern
defect have become extremely small. Therefore, the pattern
inspection apparatus for inspecting defects of ultrafine patterns
exposed/transferred onto a semiconductor wafer needs to be highly
accurate. Further, one of major factors that decrease the yield of
the LSI manufacturing is due to pattern defects on the mask used
for exposing/transferring an ultrafine pattern onto a semiconductor
wafer by the photolithography technology. Therefore, the pattern
inspection apparatus for inspecting defects on a transfer mask used
in the manufacturing LSI needs to be highly accurate.
[0004] As an inspection method, there is known a method of
comparing a measured image acquired by imaging a pattern formed on
a substrate, such as a semiconductor wafer or a lithography mask,
with design data or with another measured image acquired by imaging
the same pattern on the substrate. For example, as a pattern
inspection method, there is "die-to-die inspection" or
"die-to-database inspection". The "die-to-die inspection" method
compares data of measured images acquired by imaging the same
patterns at different positions on the same substrate. The
"die-to-database inspection" method generates, based on pattern
design data, design image data (reference image) to be compared
with a measured image being measured data acquired by imaging a
pattern. Then, acquired images are transmitted as measured data to
the comparison circuit. After performing alignment between the
images, the comparison circuit compares the measured data with
reference data according to an appropriate algorithm, and
determines that there is a pattern defect if the compared data do
not match each other.
[0005] Specifically with respect to the pattern inspection
apparatus described above, in addition to the type of apparatus
that irradiates an inspection substrate with laser beams in order
to obtain a transmission image or a reflection image of a pattern
formed on the substrate, there has been developed another
inspection apparatus that acquires a pattern image by scanning the
inspection substrate with primary electron beams and detecting
secondary electrons emitted from the inspection substrate due to
the irradiation with the primary electron beams. Not only the
single beam system that uses one electron beam but the multi-beam
system that acquires an image by using a plurality of electron
beams is also under development. Images acquired with such electron
beams include a noise component. Such a noise component can be
reduced by increasing the amount of electrons. However, if the
electron amount is increased, a target object may receive damage.
Then, it is examined to reduce the noise component by filtering.
However, in the filtering processing, since averaging
(equalization) is performed using images of different positions,
so-called blurring occurs. Therefore, it is now examined to acquire
the same images a plurality of times by repeating scanning the same
line in order to perform averaging of the image data by using the
repeated times (e.g., refer to Japanese Unexamined Patent
Publication No. 2011-003930). However, it takes long to perform a
scanning operation a plurality of times, which results in a problem
that the image acquisition time becomes long. Moreover, in the
multi-beam system, if a large variability exists among beams, there
is a stability problem in detection sensitivity when performing an
inspection using acquired images. Thus, a noise reduction problem
of images may occur not only in the inspection apparatus but also
in all the apparatuses acquiring images with electron beams.
BRIEF SUMMARY OF THE INVENTION
[0006] According to one aspect of the present invention, a
multi-charged particle beam image acquisition apparatus
includes
[0007] an image acquisition mechanism, including a stage on which a
target object is capable to be disposed and a deflector which
deflects multiple charged particle beams in an array arrangement,
configured to acquire, in a state where a scan region width to be
scanned by each beam of the multiple charged particle beams has
been set depending on an image averaging frequency, image data of
the each beam by scanning the target object with the multiple
charged particle beams deflected by the deflector while relatively
shifting an angle of a moving direction of the stage and an angle
of an array arranging direction of the multiple charged particle
beams from each other; and
[0008] an averaging circuit configured to average, using the image
data of the each beam, errors of the image data by superimposing
image data of a same position at the image averaging frequency.
[0009] According to another aspect of the present invention, a
multi-charged particle beam image acquisition method includes
[0010] acquiring, in a state where a scan region width to be
scanned by each beam of multiple charged particle beams in an array
arrangement has been set depending on an image averaging frequency,
image data of the each beam by scanning a target object disposed on
a stage with the multiple charged particle beams deflected by a
deflector while relatively shifting an angle of a moving direction
of the stage and an angle of an array arranging direction of the
multiple charged particle beams from each other; and
[0011] averaging, using the image data of the each beam, errors of
the image data by superimposing image data of a same position at
the image averaging frequency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows an example of a configuration of a pattern
inspection apparatus according to a first embodiment;
[0013] FIG. 2 is a conceptual diagram showing a configuration of a
shaping aperture array substrate according to the first
embodiment;
[0014] FIG. 3 shows an example of a plurality of chip regions
formed on a semiconductor substrate, according to the first
embodiment;
[0015] FIGS. 4A and 4B illustrate a scanning operation with
multiple beams, where FIG. 4A shows that according to a comparative
example and FIG. 4B shows that according to the first
embodiment;
[0016] FIG. 5 shows an example of an internal configuration of a
scan region setting circuit according to the first embodiment;
[0017] FIG. 6 shows an example of an internal configuration of a
correction circuit according to the first embodiment;
[0018] FIG. 7 is a flowchart showing main steps of an example of an
inspection method according to the first embodiment;
[0019] FIG. 8 illustrates an example of a scan width of each beam,
and an example of averaging processing according to the first
embodiment;
[0020] FIGS. 9A and 9B illustrate another example of a scan width
of each beam, and an example of averaging processing according to
the first embodiment;
[0021] FIGS. 10A to 10C illustrate a relation between a line scan
direction of each beam and an obtained image according to the first
embodiment;
[0022] FIG. 11 shows another example of the contents of averaging
processing according to the first embodiment;
[0023] FIG. 12 illustrates weighting processing according to the
first embodiment;
[0024] FIG. 13 shows an example of an internal configuration of a
comparison circuit according to the first embodiment;
[0025] FIGS. 14A and 14B illustrate scanning operations with
multiple beams according to a second embodiment;
[0026] FIGS. 15A and 15B illustrate scanning operations with
multiple beams according to a third embodiment;
[0027] FIGS. 16A and 16B illustrate scanning operations with
multiple beams according to a fourth embodiment;
[0028] FIGS. 17A and 17B illustrate scanning operations with
multiple beams according to a fifth embodiment;
[0029] FIG. 18 illustrates scanning operations with multiple beams
according to a sixth embodiment; and
[0030] FIGS. 19A and 19B illustrate scanning operations with
multiple beams according to the seventh embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Embodiments below describe an image acquisition apparatus
and method that can reduce a noise, based on averaging processing
corresponding to a necessary frequency (the number of times) used
for averaging when acquiring an image with multiple beams, without
repeatedly scanning the same position the number of times needed as
the averaging frequency.
First Embodiment
[0032] FIG. 1 shows an example of a configuration of a pattern
inspection apparatus according to a first embodiment. In FIG. 1, an
inspection apparatus 100 for inspecting patterns formed on a
substrate is an example of a multi electron beam inspection
apparatus. The inspection apparatus 100 includes an image
acquisition mechanism 150 (secondary electron image acquisition
mechanism) and a control system circuit 160. The image acquisition
mechanism 150 includes an electron beam column 102 (also called an
electron optical column) and an inspection chamber 103. In the
electron beam column 102, there are disposed an electron gun 201,
an electromagnetic lens 202, a shaping aperture array substrate
203, an electromagnetic lens 205, a common blanking deflector 212,
a limiting aperture substrate 213, an electromagnetic lens 206, an
electromagnetic lens 207 (objective lens), a main deflector 208, a
sub deflector 209, a beam separator 214, a deflector 218, an
electromagnetic lens 224, an electromagnetic lens 226, and a
multi-detector 222. In the case of FIG. 1, a primary electron
optical system that irradiates a substrate 101 with multiple
primary electron beams 20 is composed of the electron gun 201, the
electromagnetic lens 202, the shaping aperture array substrate 203,
the electromagnetic lens 205, the common blanking deflector 212,
the limiting aperture substrate 213, the electromagnetic lens 206,
the electromagnetic lens 207 (objective lens), the main deflector
208, and the sub deflector 209. A secondary electron optical system
that irradiates the multi-detector 222 with multiple secondary
electron beams 300 is composed of the beam separator 214, the
deflector 218, the electromagnetic lens 224, and the
electromagnetic lens 226. Further, it is also preferable to dispose
an electrostatic lens 215 that can rotate a multiple primary
electron beam image, in the magnetic field of the electromagnetic
lens 206.
[0033] A stage 105 movable at least in the x and y directions is
disposed in the inspection chamber 103. The substrate 101 (target
object) to be inspected is mounted on the stage 105. The substrate
101 may be an exposure mask substrate, or a semiconductor substrate
such as a silicon wafer. In the case of the substrate 101 being a
semiconductor substrate, a plurality of chip patterns (wafer dies)
are formed on the semiconductor substrate. In the case of the
substrate 101 being an exposure mask substrate, a chip pattern is
formed on the exposure mask substrate. The chip pattern is composed
of a plurality of figure patterns. If the chip pattern formed on
the exposure mask substrate is exposed/transferred onto the
semiconductor substrate a plurality of times, a plurality of chip
patterns (wafer dies) are formed on the semiconductor substrate.
The case of the substrate 101 being a semiconductor substrate is
described below mainly. The substrate 101 is placed with its
pattern-forming surface facing upward on the stage 105, for
example. Moreover, on the stage 105, there is disposed a mirror 216
which reflects a laser beam for measuring a laser length emitted
from a laser length measuring system 122 arranged outside the
inspection chamber 103. The multi-detector 222 is connected, at the
outside of the electron beam column 102, to a detection circuit
106.
[0034] In the control system circuit 160, a control computer 110
which controls the whole of the inspection apparatus 100 is
connected, through a bus 120, to a position circuit 107, a
comparison circuit 108, a reference image generation circuit 112, a
stage control circuit 114, a lens control circuit 124, a blanking
control circuit 126, a deflection control circuit 128, a scan
region setting circuit 140, an image correction circuit 141, a
storage device 109 such as a magnetic disk drive, a monitor 117, a
memory 118, and a printer 119. The deflection control circuit 128
is connected to DAC (digital-to-analog conversion) amplifiers 144,
146 and 148. The DAC amplifier 146 is connected to the main
deflector 208, and the DAC amplifier 144 is connected to the sub
deflector 209. The DAC amplifier 148 is connected to the deflector
218.
[0035] The detection circuit 106 is connected to a chip pattern
memory 123 which is connected to the image correction circuit 141.
The stage 105 is driven by a drive mechanism 142 under the control
of the stage control circuit 114. In the drive mechanism 142, a
drive system such as a three (x-, y-, and .theta.-) axis motor
which provides drive in the directions of x, y, and 0 in the stage
coordinate system is configured, and the stage 105 can move in the
x, y, and .theta. directions. A step motor, for example, can be
used as each of these x, y, and .theta. motors (not shown). The
stage 105 is movable in the horizontal direction and the rotation
direction by the x-, y-, and .theta.-axis motors. The moving
position of the stage 105 is measured by the laser length measuring
system 122, and supplied (transmitted) to the position circuit 107.
Based on the principle of laser interferometry, the laser length
measuring system 122 measures the position of the stage 105 by
receiving a reflected light from the mirror 216.
[0036] The electromagnetic lenses 202, 205, 206, 207 (objective
lens), 224 and 226, and the beam separator 214 are controlled by
the lens control circuit 124. The common blanking deflector 212 is
configured by two or more electrodes (or "two or more poles"), and
each electrode is controlled by the blanking control circuit 126
through a DAC amplifier (not shown). The sub deflector 209 is
configured by four or more electrodes (or "four or more poles"),
and each electrode is controlled by the deflection control circuit
128 through the DAC amplifier 144. The main deflector 208 is
configured by four or more electrodes (or "four or more poles"),
and each electrode is controlled by the deflection control circuit
128 through the DAC amplifier 146. The deflector 218 is configured
by four or more electrodes (or "four or more poles"), and each
electrode is controlled by the deflection control circuit 128
through the DAC amplifier 146. When the electrostatic lens 215 is
disposed, a lens control circuit (not shown) is arranged.
[0037] To the electron gun 201, there is connected a high voltage
power supply circuit (not shown). The high voltage power supply
circuit applies an acceleration voltage between a filament
(cathode) and an extraction electrode (anode) (which are not shown)
in the electron gun 201. In addition to the applying the
acceleration voltage, applying a voltage to another extraction
electrode (Wehnelt) and heating the cathode to a predetermined
temperature are performed, and thereby, electrons from the cathode
are accelerated to be emitted as an electron beam 200.
[0038] FIG. 1 shows configuration elements necessary for describing
the first embodiment. It should be understood that other
configuration elements generally necessary for the inspection
apparatus 100 may also be included therein.
[0039] FIG. 2 is a conceptual diagram showing a configuration of a
shaping aperture array substrate according to the first embodiment.
As shown in FIG. 2, holes (openings) 22 of m.sub.1 rows long
(length in the y direction) (each row in the x direction) and
n.sub.1 columns wide (width in the x direction) (each column in the
y direction) are two-dimensionally formed at a predetermined
arrangement pitch in the shaping aperture array substrate 203,
where one of m.sub.1 and n.sub.1 is an integer of 2 or more, and
the other is an integer of 1 or more. In the case of FIG. 2,
23.times.23 holes (openings) 22 are formed. Ideally, each of the
holes 22 is a rectangle (including a square) having the same
dimension, shape, and size. Alternatively, ideally, each of the
holes 22 may be a circle with the same outer diameter.
m.sub.1.times.n.sub.1 (=N) multiple primary electron beams 20 are
formed by letting portions of the electron beam 200 individually
pass through a corresponding one of a plurality of holes 22.
[0040] Next, operations of the image acquisition mechanism 150 in
the inspection apparatus 100 will be described below.
[0041] The electron beam 200 emitted from the electron gun 201
(emission source) is refracted by the electromagnetic lens 202, and
illuminates the whole of the shaping aperture array substrate 203.
As shown in FIG. 2, a plurality of holes 22 (openings) are formed
in the shaping aperture array substrate 203. The region including
all the plurality of holes 22 is irradiated by the electron beam
200. The multiple primary electron beams 20 are formed by letting
portions of the electron beam 200, which irradiate the positions of
a plurality of holes 22, individually pass through a corresponding
one of the plurality of holes 22 in the shaping aperture array
substrate 203.
[0042] The formed multiple primary electron beams 20 are
individually refracted by the electromagnetic lenses 205 and 206,
and travel to the electromagnetic lens 207 (objective lens) while
repeating forming an intermediate image and a crossover through the
beam separator 214 disposed at the crossover position of each beam
of the multiple primary electron beams 20. Then, the
electromagnetic lens 207 focuses the multiple primary electron
beams 20 onto the substrate 101. The multiple primary electron
beams 20 having been focused on the substrate 101 (target object)
by the electromagnetic lens 207 (objective lens) are collectively
deflected by the main deflector 208 and the sub deflector 209 to
irradiate respective beam irradiation positions on the substrate
101. When all of the multiple primary electron beams 20 are
collectively deflected by the common blanking deflector 212, they
deviate from the hole in the center of the limiting aperture
substrate 213 and blocked by the limiting aperture substrate 213.
On the other hand, the multiple primary electron beams 20 which
were not deflected by the common blanking deflector 212 pass
through the hole in the center of the limiting aperture substrate
213 as shown in FIG. 1. Blanking control is provided by On/Off of
the common blanking deflector 212 to collectively control On/Off of
the multiple beams. Thus, the limiting aperture substrate 213
blocks the multiple primary electron beams 20 which were deflected
to be in the "Off condition" by the common blanking deflector 212.
Then, the multiple primary electron beams 20 for inspection (for
image acquisition) are formed by the beams having been made during
a period from becoming "beam On" to becoming "beam Off" and having
passed through the limiting aperture substrate 213.
[0043] When desired positions on the substrate 101 are irradiated
with the multiple primary electron beams 20, a flux of secondary
electrons (multiple secondary electron beams 300) including
reflected electrons each corresponding to each of the multiple
primary electron beams 20 is emitted from the substrate 101 due to
the irradiation by the multiple primary electron beams 20.
[0044] The multiple secondary electron beams 300 emitted from the
substrate 101 travel to the beam separator 214 through the
electromagnetic lens 207.
[0045] The beam separator 214 generates an electric field and a
magnetic field to be perpendicular to each other in a plane
perpendicular to the traveling direction (electron orbit central
axis) of the center beam of the multiple primary electron beams 20.
The electric field affects (exerts a force) in the same fixed
direction regardless of the traveling direction of electrons. In
contrast, the magnetic field affects (exerts a force) according to
Fleming's left-hand rule. Therefore, the direction of force acting
on (applied to) electrons can be changed depending on the traveling
(or "entering") direction of the electrons. With respect to the
multiple primary electron beams 20 entering the beam separator 214
from the upper side, since the force due to the electric field and
the force due to the magnetic field cancel each other out, the
multiple primary electron beams 20 travel straight downward. In
contrast, with respect to the multiple secondary electron beams 300
entering the beam separator 214 from the lower side, since both the
force due to the electric field and the force due to the magnetic
field are exerted in the same direction, the multiple secondary
electron beams 300 are bent obliquely upward, and separated from
the multiple primary electron beams 20.
[0046] The multiple secondary electron beams 300 having been bent
obliquely upward and separated from the multiple primary electron
beams 20 are further bent by the deflector 218, and projected,
while being refracted, onto the multi-detector 222 by the
electromagnetic lenses 224 and 226. The multi-detector 222 detects
the projected multiple secondary electron beams 300. It is
acceptable that reflected electrons and secondary electrons are
projected on the multi-detector 222, or that reflected electrons
are emitted on the way and remaining secondary electrons are
projected. The multi-detector 222 includes a two-dimensional sensor
(to be described later). Each secondary electron of the multiple
secondary electron beams 300 collides with a corresponding region
of the two-dimensional sensor so as to generate an electron and
secondary electron image data for each pixel. In other words, in
the multi-detector 222, a detection sensor is disposed for each
primary electron beam i of the multiple primary electron beams 20,
where i=1 to 529 in the case of the multiple primary electron beams
20 being composed of 23.times.23 beams. Then, the detection sensor
detects a corresponding secondary electron beam emitted by
irradiation with the primary electron beam i. Therefore, each of a
plurality of detection sensors in the multi-detector 222 detects an
intensity signal of a secondary electron beam for an image, which
is resulting from irradiation with a corresponding primary electron
beam 10. The intensity signal detected by the multi-detector 222 is
output to the detection circuit 106.
[0047] FIG. 3 shows an example of a plurality of chip regions
formed on a semiconductor substrate, according to the first
embodiment. In FIG. 3, in the case of the substrate 101 being a
semiconductor substrate (wafer), a plurality of chips (wafer dies)
332 in a two-dimensional array are formed in an inspection region
330 of the semiconductor substrate (wafer). A mask pattern for one
chip formed on an exposure mask substrate is reduced to 1/4, for
example, and exposed/transferred onto each chip 332 by an exposure
device (stepper) (not shown). The region of each chip 332 is
divided into a plurality of stripe regions 32 by a predetermined
width being in the y direction, for example. The scanning operation
by the image acquisition mechanism 150 is carried out for each
stripe region 32, for example. The operation of scanning the stripe
region 32 advances relatively in the x direction while the stage
105 is moved in the -x direction, for example.
[0048] FIGS. 4A and 4B illustrate a scanning operation with
multiple beams, where FIG. 4A shows that according to a comparative
example and FIG. 4B shows that according to the first embodiment.
FIGS. 4A and 4B show the case of the multiple primary electron
beams 20 of 3.times.3 (rows by columns). FIG. 4A shows a
comparative example of the first embodiment, wherein the size of an
irradiation region 34 that can be irradiated by one irradiation
with the multiple primary electron beams 20 is defined by (x
direction size obtained by multiplying a beam pitch in the x
direction of the multiple primary electron beams 20 on the
substrate 101 by the number of beams in the x direction).times.(y
direction size obtained by multiplying a beam pitch in the y
direction of the multiple primary electron beams 20 on the
substrate 101 by the number of beams in the y direction).
Preferably, the width of each stripe region 32 is set to be the
same as the size in the y direction of the irradiation region 34,
or to be the size reduced by the width of the scanning margin. In
the example of FIG. 4A, each beam of the multiple primary electron
beams 20 scans the inside of a sub-irradiation region 29 concerned
surrounded by the beam pitch in the x direction and the beam pitch
in the y direction where the beam concerned itself is located
therein. For example, the scanning operation proceeds in the x
direction being the scanning direction while repeating a line
scanning in the y direction. Each primary electron beam 10 of the
multiple primary electron beams 20 is associated with any one of
the sub-irradiation regions 2 to 9 which are different from each
other. At the time of each shot, each primary electron beam 10 is
applied to the same position in the associated sub-irradiation
region 29 concerned. The primary electron beam 10 is moved in the
sub-irradiation region 29 by collective deflection of all the
multiple primary electron beams 20 by the sub deflector 209. By
repeating this operation, the inside of one sub-irradiation region
29 is irradiated, in order, with one primary electron beam 10.
Then, when scanning of one sub-irradiation region 29 is completed,
the irradiation position is moved to a rectangular (including
square) region 33, which is the same size as the irradiation region
34, in the same stripe region 32 by collectively deflecting all the
multiple primary electron beams 20 by the main deflector 208. By
repeating this operation, the inside of the stripe region 32 is
irradiated in order. In this scanning operation, each region is
scanned only once by any one of the beams. However, if this
operation is continued, difference is generated among acquired
images due to difference of a noise component of each beam. Then,
for example, according to a comparative example, after scanning one
sub irradiation region 29, the sub irradiation region 29 adjacent
in the x direction, for example, is scanned by continuously moving
the stage 105. By this, the same position can be overlappingly
scanned by three beams aligned in the x direction. Thereby, the
image of the same region can be overlappingly obtained by different
three beams without repeatedly scanning the same line a plurality
of times. Then, averaging (equalization) can be performed by
overlapping three images of the same region. Therefore, averaging
can be performed for images obtained a plurality of times being the
same number as the number of beams aligned in the x direction.
However, according to this method, the frequency (the number of
times) used for averaging (hereinafter, sometimes referred as an
averaging frequency) is always limited to the number of beams
aligned in the x direction. Therefore, depending on conditions,
image averaging may be performed based on the number which is more
than needed or less than needed. Accordingly, it is desirable to
arbitrarily set the frequency (the number of times) used for
averaging. Further, according to this method, the region located at
the end (boundary) of an image, which is obtained by each beam, is
always located at the end (boundary) of the images even obtained by
the other two beams aligned in the x direction. Therefore, since
image boundaries are always overlapped with each other even in the
case of averaging, difference (deviation) occurs easily at the
connecting portion (boundary)) of adjacent images.
[0049] Then, according to the first embodiment, as shown in FIG.
4B, the angle of the moving direction of the stage 105 and the
angle of the arranging direction of the multiple primary electron
beams 20 are relatively shifted from each other so that a plurality
of the primary electron beams 10 of the multiple primary electron
beams 20 may not be arranged in parallel to the moving direction of
the stage 105. For example, the arrangement angle of the shaping
aperture array substrate 203 is rotated to shift them from each
other. Alternatively, the moving direction of the stage 105 is
adjusted to be oblique instead of the -x direction, for example.
Alternatively, it is also preferable to rotate the multiple primary
electron beam image on the substrate 101 by using the electrostatic
lens 215. The tilt angle .theta. (rad) can be defined by the
following equation (1) using a value obtained by dividing the beam
pitch in the y direction of the multiple primary electron beams 20
by a value obtained by multiplying the beam pitch in the x
direction by the number of beams in the x direction.
.theta.=tan.sup.-1(beam pitch in y direction/(beam pitch in x
direction.times.the number of beams in x direction)) (1)
[0050] In the example of FIG. 4B, a plurality of the primary
electron beams 10 of the multiple primary electron beams 20 can be
arranged not to be parallel to the moving direction of the stage
105 by rotating the arranging direction of the multiple primary
electron beams 20 of 3.times.3 (rows by columns) on the substrate
101 by the tilt angle .theta.. Thereby, an individual scan region
27 to be scanned by each primary electron beam 10 can be set, as
shown in FIG. 4B, on the substrate 101 which extends in parallel to
the moving direction of the stage 105. In the case of the multiple
primary electron beams 20 of 3.times.3 (rows by columns), the
individual scan region 27 can be set for each of the beams 1 to 9.
In FIG. 4B, the stripe region 32 in the x direction is divided into
nine individual scan regions 27(1) to (9) in a strip form by the
same width in the y direction. Referring to FIG. 4B, description is
given on the basis that there are n primary electron beams 10 each
of which scans the individual scan region 27 (n) of a certain
stripe region 32 (n being an integer from 1 to 9). Then, if the
scan region width to be scanned by each primary electron beam 10 is
the same as the width of the individual scan region 27, which
results in that each beam individually acquires an image of a
separate region, thereby being impossible to perform averaging.
According to the first embodiment, the scan region width to be
scanned by each primary electron beam 10 is set variably.
[0051] FIG. 5 shows an example of an internal configuration of the
scan region setting circuit 140 according to the first embodiment.
In FIG. 5, in the scan region setting circuit 140, there are
arranged an averaging frequency setting unit 60, a line scan
direction setting unit 61, an individual region setting unit 62,
and a scan width setting unit 64. Each of the "units" such as the
averaging frequency setting unit 60, the line scan direction
setting unit 61, the individual region setting unit 62, and the
scan width setting unit 64 includes processing circuitry. As the
processing circuitry, for example, an electric circuit, computer,
processor, circuit board, quantum circuit, semiconductor device, or
the like can be used. Moreover, each of the "units" may use common
processing circuitry (the same processing circuitry), or different
processing circuitry (separate processing circuitry). Input data
needed in the averaging frequency setting unit 60, the line scan
direction setting unit 61, the individual region setting unit 62,
and the scan width setting unit 64, and calculated results are
stored in a memory (not shown) or in the memory 118 each time.
[0052] FIG. 6 shows an example of an internal configuration of the
image correction circuit 141 according to the first embodiment. In
FIG. 6, in the image correction circuit 141, there are arranged a
memory 71, a plurality of gain correction units 70 (a to n)
corresponding to the number of beams of the multiple primary
electron beams 20, a plurality of buffers 72 (a to n) corresponding
to the number of beams, a plurality of alignment units 74 (a to n)
corresponding to the number of beams, an averaging unit 76, and a
storage devices 79, such as a magnetic disk drive for storing a
corrected image. In the averaging unit 76, there are arranged an
addition unit 77 and a division unit 78. Each of the "units" such
as a plurality of gain correction units 70 (a to n), a plurality of
buffers 72 (a to n), a plurality of alignment units 74 (a to n),
and the averaging unit 76 (the addition unit 77 and the division
unit 78) includes processing circuitry. As the processing
circuitry, for example, an electric circuit, computer, processor,
circuit board, quantum circuit, semiconductor device, or the like
can be used. Moreover, each of the "units" may use common
processing circuitry (the same processing circuitry), or different
processing circuitry (separate processing circuitry). Input data
needed in a plurality of gain correction units 70(a to n), a
plurality of buffers 72 (a to n), a plurality of alignment units 74
(a to n), and the averaging unit 76 (the addition unit 77 and the
division unit 78), and calculated results are stored in the memory
71 or the memory 118 in FIG. 1 each time. As for a plurality of
gain correction units 70, it is desirable to dispose them, but they
may be omitted.
[0053] FIG. 7 is a flowchart showing main steps of an example of an
inspection method according to the first embodiment. In FIG. 7, the
inspection method of the first embodiment executes a series of
steps: a parameter setting step (S102), an individual region
setting step (S104), a scan width setting step (S106), a scanning
step (S108), a moving in stripe-regions step (S110), a weighting
step (S120), an averaging step (S122), and a comparison step
(S130). The averaging step (S122) carries out an addition step
(S124) and a division step (S126) as internal steps. As for the
weighting step (S120), it is desirable to dispose it, but it may be
omitted.
[0054] In the parameter setting step (S102), the averaging
frequency setting unit 60 sets, as one of parameters, an image
averaging frequency (that is, the frequency (the number of times)
used for image averaging). The image averaging frequency (the
number of times) can be variably set from one to the number of
beams of the multiple primary electron beams 20. However, in the
case of the image averaging frequency being one, since it does not
change from the original image, it cannot be said that this state
has been averaged. Therefore, here, it is variably set from two to
the number of beams of the multiple primary electron beams. For
example, if the multiple primary electron beams 20 of 3.times.3 can
be applied, the image averaging frequency can be variably set from
two to nine. Moreover, the line scan direction setting unit 61
sets, as another parameter, the line scan direction of each beam.
Here, as shown in FIG. 4B, the line scan direction of each beam is
set to be the y direction, for example, without shifting (rotating)
it by the tilt angle .theta..
[0055] In the individual region setting step (S104), the individual
region setting unit 62 sets the individual scan region 27 of each
beam on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. In FIG. 4B, the stripe region 32 in the x direction is
divided into nine individual scan regions 27(1) to (9) in a strip
form by the same width in the y direction.
[0056] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual scan regions
27 of other beams may be included in the direction perpendicular to
the moving direction of the stage 105. The scan width setting unit
64 sets the scan region width to be scanned by each primary
electron beam 10 of the multiple primary electron beams 20 to be
variable correspondingly depending on the image averaging frequency
which can be set variably. In other words, depending on
(corresponding to) the frequency used for image averaging, the scan
region width in the y direction of each primary electron beam 10 is
expanded. When the frequency used for image averaging is nine which
is the maximum number of beams of the multiple primary electron
beams 20, the scan region width in the y direction of each primary
electron beam 10 needs to be equivalent to the width of nine
individual scan regions 27 so as to be scanned. Thus, it is
necessary for each primary electron beam 10 to scan at least this
width (the width of nine individual scan regions 27).
[0057] FIG. 8 illustrates an example of a scan width of each beam,
and an example of averaging processing according to the first
embodiment. FIG. 8 shows the case of using the multiple primary
electron beams 20 of 3.times.3 and the image averaging frequency
being three. When the image averaging frequency (that is, the
frequency used for image averaging) is three, the scan width
(individual beam scan width) of each primary electron beam 10 is
set to be the width in the y direction of the total of three
individual scan regions 27 including the individual scan region 27
currently concerned and two adjacent individual scan regions 27 of
the primary electron beam 10. In the example of FIG. 8, the scan
width of each primary electron beam 10 is set to be the width in
the y direction of the total of three individual scan regions 27
including the individual scan region 27 currently concerned, the
second individual scan region 27, being adjacent in the y
direction, and the third individual scan region 27, being further
in the y direction. Therefore, the beam 1 scans three individual
scan regions 27(1) to (3) of the k-th stripe region 32. The beam 2
scans three individual scan regions 27(2) to (4) of the k-th stripe
region 32. The beam 3 scans three individual scan regions 27(3) to
(5) of the k-th stripe region 32. The beam 4 scans three individual
scan regions 27(4) to (6) of the k-th stripe region 32. The beam 5
scans three individual scan regions 27(5) to (7) of the k-th stripe
region 32. The beam 6 scans three individual scan regions 27(6) to
(8) of the k-th stripe region 32. The beam 7 scans three individual
scan regions 27(7) to (9) of the k-th stripe region 32. The beam 8
scans three individual scan regions 27(8), (9), and (1) which are
two individual scan regions 27(8) and (9) of the k-th stripe region
32, and one individual scan region 27(1) of the (k+1)th stripe
region 32. The beam 9 scans three regions 27(9), (1), and (2) which
are one individual scan region 27(9) of the k-th stripe region 32,
and two individual scan regions 27(1) and (2) of the (k+1)th stripe
region 32. Therefore, the scan width (multiple beam scan width) of
the whole of the multiple primary electron beams 20 is the width in
the y direction of the total of eleven individual scan regions 27
which are obtained by adding the width of the stripe region 32
concerned and two individual scan regions 27 of the next stripe
region 32.
[0058] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105.
[0059] For acquiring an image, as described above, the multiple
primary electron beams 20 are applied to the substrate 101 so that
the multi-detector 222 may detect the multiple secondary electron
beams 300 emitted from the substrate 101 by the irradiation with
the multiple primary electron beams 20. Detected data (measured
image data: secondary electron image data: inspection image data)
on a secondary electron of each beam detected by the multi-detector
222 is output to the detection circuit 106 in order of measurement.
In the detection circuit 106, the detected data in analog form is
converted into digital data by an A-D converter (not shown), and
stored in the chip pattern memory 123. Then, acquired measured
image data is transmitted to the image correction circuit 141,
together with information on each position from the position
circuit 107. As shown in FIG. 8, by scanning with each beam, image
data for each of three individual scan regions 27 is output to the
image correction circuit 141 per one beam scanning.
[0060] In the moving in stripe-regions step (S110), after
completing scanning one stripe region 32, the stage 105 is moved to
the starting position of the next scanning operation in the
adjacent next stripe region 32. Then, it returns to the scanning
step (S108) to perform a scanning operation similarly.
[0061] Thereby, as shown in FIG. 8, by the operation of scanning
the k-th stripe region 32, image data (secondary electron image
data) in the individual scan region (1) of the k-th stripe region
32 is acquired by the scanning with the beam 1. Image data in the
individual scan region (2) of the k-th stripe region 32 is
overlappingly acquired by the scanning with the beams 1 and 2.
Image data in the individual scan region (3) of the k-th stripe
region 32 is overlappingly acquired by the scanning with the beams
1 to 3. Image data in the individual scan region (4) of the k-th
stripe region 32 is overlappingly acquired by the scanning with the
beams 2 to 4. Image data in the individual scan region (5) of the
k-th stripe region 32 is overlappingly acquired by the scanning
with the beams 3 to 5. Image data in the individual scan region (6)
of the k-th stripe region 32 is overlappingly acquired by the
scanning with the beams 4 to 6. Image data in the individual scan
region (7) of the k-th stripe region 32 is overlappingly acquired
by the scanning with the beams 5 to 7. Image data in the individual
scan region (8) of the k-th stripe region 32 is overlappingly
acquired by the scanning with the beams 6 to 8. Image data in the
individual scan region (9) of the k-th stripe region 32 is
overlappingly acquired by the scanning with the beams 7 to 9. Image
data in the individual scan region (1) of the (k+1)th stripe region
32 is overlappingly acquired by the scanning with the beams 8 and
9. Image data in the individual scan region (2) of the (k+1)th
stripe region 32 is overlappingly acquired by the scanning with the
beam 9.
[0062] Therefore, as shown in FIG. 8, in each of the individual
scan regions 27(3) to (9), three pieces of image data are obtained
overlappingly with three beams. By performing the operation of
scanning the k-th stripe region 32, only one image data by one beam
can be obtained with respect to the individual scan region (1) of
the k-th stripe region 32. Similarly, by the operation of scanning
the k-th stripe region 32, only two pieces of image data by two
beams can be obtained with respect to the individual scan region
(2) of the k-th stripe region 32. However, by performing the
operation of scanning the (k-1)th stripe region 32, two pieces of
image data by two beams have already been overlappingly obtained
with respect to the individual scan region (1) of the k-th stripe
region 32. Similarly, by the operation of scanning the (k-1)th
stripe region 32, one image data by one beam has already been
obtained with respect to the individual scan region (2) of the k-th
stripe region 32. Thus, insufficient image data for the individual
scan region 27 at the end of each stripe region 32 can be acquired
by the operation of scanning the adjacent (prior) stripe region 32.
Accordingly, three pieces of image data can be overlappingly
obtained with respect to each of all the individual scan regions
27.
[0063] In the averaging step (S122), using image data of each beam,
the averaging unit 76 in the image correction circuit 141 averages
errors of the image data by superimposing image data of the same
position at the number being the same as that indicated by an image
averaging frequency having been set. Specifically, the image data
of each beam is stored in the buffer 72 for each beam. When the
same individual scan region 27 is scanned by a plurality of beams,
since a time difference occurs in scanning time, the image data of
each beam is temporarily stored in the buffer 72. Then, the image
data is output to the alignment unit 74 for each beam. The
alignment unit 74 for each beam provides alignment with image data
of other beams which scanned the same individual scan region 27.
Specifically, deviation in the y direction is corrected. Then, each
image data whose alignment has been performed is output to the
averaging unit 76. In the averaging unit 76, in the addition step
(S124), the addition unit 77 adds (integrates) gray-scale level
values of image data of the same position at the number being the
same as that indicated by the image averaging frequency having been
set. Then, in the division step (S126), the division unit 78
divides the added gray-scale level values of the image data by the
image averaging frequency (the number of times). In the example of
FIG. 8, since three pieces of image data have been acquired for
each individual scan region 27, the addition unit 77 adds
(integrates) these image data, and then, the division unit 78
divides the added image data by three. Thereby, it is possible to
obtain an image which has been averaged by using the image
averaging frequency being three. Although, here, after performing
the addition, the division is performed using the image averaging
frequency, it is not limited thereto. It is also preferable to
perform only addition. The averaged image data of each individual
scan region 27 is output to the comparison circuit 108.
[0064] Regarding each individual scan region 27, three pieces of
image data can be acquired. Specifically, image data of one
individual scan region 27 located at the end of three individual
scan regions 27 scanned by one beam, image data of another
individual scan region 27 located in the center of the three
individual scan regions 27 scanned by the one beam, and image data
of another individual scan region 27 located at the other end of
the three individual scan regions 27 scanned by the one beam. For
example, in the individual scan region (3), it is possible to
acquire three pieces of image data scanned at different scanning
positions, that is, the image data scanned by the beam 1 at one end
of the scan region width, the image data scanned by the beam 2 at
the center of the scan region width, and the image data scanned by
the beam 3 at the other end of the scan region width. In other
words, with respect to image data to be combined, the beam
connecting portion can be distributed (decentralized). Thus,
difference due to deviation of gray-scale level values at the beam
connecting portion (image boundary) between mutually adjacent
individual scan regions 27 is unlikely to occur. Accordingly,
compared to the case of averaging using data at the image boundary
performed at the position of the image boundary shown in FIG. 4A,
according to the first embodiment, since the three pieces of image
data at different scanning positions are integrated, the influence
of difference due to deviation of gray-scale level values at the
beam connecting portion (boundary)) between mutually adjacent
individual scan regions 27 can be reduced.
[0065] FIGS. 9A and 9B illustrate another example of a scan width
of each beam, and an example of averaging processing according to
the first embodiment. FIGS. 9A and 9B show the case of using the
multiple primary electron beams 20 of 3.times.3 and the image
averaging frequency being nine. When the image averaging frequency
(that is, the frequency used for image averaging) is nine, the scan
width (individual beam scan width) of each primary electron beam 10
is set to be the width in the y direction of the total of nine
individual scan regions 27 including the individual scan region 27
currently concerned and eight individual scan regions 27, each
adjacent in the y direction, of the primary electron beam 10.
Therefore, as shown in FIG. 9A, when scanning the k-th stripe
region 32, the beam 1 scans nine individual scan regions 27(1) to
(9) of the k-th stripe region 32. The beam 2 scans eight individual
scan regions 27(2) to (9) of the k-th stripe region 32 and one
individual scan region 27(1) of the (k+1)th stripe region 32. The
beam 3 scans seven individual scan regions 27(3) to (9) of the k-th
stripe region 32 and two individual scan regions 27(1) and (2) of
the (k+1)th stripe region 32. The beam 4 scans six individual scan
regions 27(4) to (9) of the k-th stripe region 32 and three
individual scan regions 27(1) to (3) of the (k+1)th stripe region
32. The beam 5 scans five individual scan regions 27(5) to (9) of
the k-th stripe region 32 and four individual scan regions 27(1) to
(4) of the (k+1)th stripe region 32. The beam 6 scans four
individual scan regions 27(6) to (9) of the k-th stripe region 32
and five individual scan regions 27(1) to (5) of the (k+1)th stripe
region 32. The beam 7 scans three individual scan regions 27(7) to
(9) of the k-th stripe region 32 and six individual scan regions
27(1) to (6) of the (k+1)th stripe region 32. The beam 8 scans two
individual scan regions 27(8) and (9) of the k-th stripe region 32
and seven individual scan regions 27(1) to (7) of the (k+1)th
stripe region 32. The beam 9 scans one individual scan region 27(9)
of the k-th stripe region 32 and eight individual scan regions
27(1) to (8) of the (k+1)th stripe region 32. Therefore, the scan
width (multiple beam scan width) of the whole of the multiple
primary electron beams 20 is the width in the y direction of the
total of eighteen individual scan regions 27 which are obtained by
adding the width of the stripe region 32 concerned and nine
individual scan regions 27 of the next stripe region 32. In other
words, the scan width (multiple beam scan width) of the whole of
the multiple primary electron beams 20 is the width in the y
direction of two stripe regions 32. As shown in FIG. 9B, image data
of nine individual scan regions 27 by each one beam scanning is
output to the image correction circuit 141.
[0066] Therefore, as shown in FIGS. 9A and 9B, in each individual
scan regions 27, nine pieces of image data are overlappingly
obtained with nine beams. With respect to each individual scan
region 27 of the k-th stripe region 32, insufficient image data
which cannot be obtained by scanning the k-th stripe region 32 can
be compensated by being combined with image data obtained by
scanning the (k-1)th stripe region 32. This relation is satisfied
in the case of setting the image averaging frequency to be any one
from two to the number of beams of the multiple primary electron
beams.
[0067] Using image data of each beam, the averaging unit 76 in the
image correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set. In the case of FIGS. 9A and 9B, since nine pieces of
image data have been acquired for each individual scan region 27,
the addition unit 77 adds (integrates) these image data, and then,
the division unit 78 divides the added image data by nine. Thereby,
it is possible to obtain an image which has been averaged by using
the image averaging frequency being nine. The averaged image data
of each individual scan region 27 is output to the comparison
circuit 108.
[0068] Although the above examples describe the case where each
beam performs a scanning operation whose line scan direction is the
y direction, it is not limited thereto.
[0069] FIGS. 10A to 100 illustrate a relation between a line scan
direction of each beam and an obtained image according to the first
embodiment. FIG. 10A shows the case where the multiple primary
electron beams 20 of 3.times.3 are used. The arranging direction of
the multiple primary electron beams 20 is rotated by the tilt angle
.theta. with respect to the moving direction of the stage 105. If
setting the line scan direction of each primary electron beam 10 to
be the y direction to perform line scanning, images arranged in the
y direction are obtained as shown in FIG. 10C. On the other hand,
if setting the line scan direction of each primary electron beam 10
to be the direction rotated by 45 degrees from the y direction to
perform line scanning, images arranged in the direction rotated by
-45 degrees from the y direction as shown in FIG. 10B are obtained
due to a time delay corresponding to the order of measurement of
each pixel. However, as shown in FIG. 10C, the images can be
straightly aligned in the y direction by performing position
correction. Therefore, the line scan direction of each primary
electron beam 10 may be set arbitrarily, not restricted to the y
direction. For example, since the arranging direction of the
multiple primary electron beams 20 has been shifted by the tilt
angle .theta. with respect to the moving direction of the stage
105, the line scan direction can also be shifted from the y
direction by the tilt angle .theta..
[0070] FIG. 11 shows another example of the contents of averaging
processing according to the first embodiment. FIG. 11 shows the
case in which weighting processing by the gain correction unit 70
is further carried out in the weighting step (S120). In the image
correction circuit 141, a group of the gain correction unit 70, the
buffer 72, and the alignment unit 74 is arranged for each primary
electron beam 10. As shown in FIG. 8, when the image averaging
frequency (that is, the number of times used for image averaging)
is three, image data of each pixel in the individual scan regions
(1) to (3) is included in the image data scanned by the beam 1.
Similarly, image data of each pixel in the individual scan regions
(2) to (4) is included in the image data scanned by the beam 2.
Similarly, image data scanned by each of the beams 3 to 9 includes
image data of each pixel in the total of three individual scan
regions which are the individual scan region 27 currently concerned
and two contiguous individual scan regions. Then, the image data
obtained with each beam is output to the image correction circuit
141, and input to the gain correction unit 70 for each beam.
[0071] In the weighting step (S120), the gain correction unit 70
for each beam applies weighting to the input image data of the
three individual scan regions.
[0072] FIG. 12 illustrates weighting processing according to the
first embodiment. As shown in FIG. 12, the gain correction unit 70
for each beam applies weighting to the input image data of the
three individual scan regions so that gray-scale level values of
image data of the two individual scan regions at the both sides in
the three individual scan regions may become smaller toward the
end. Specifically, gain adjustment is performed so that a gain of a
terminal end may be reduced. Deviation at the connecting portion of
an image can be reduced or eliminated by making the weighting at
the end portion small. In other words, the influence of beam
difference can be reduced by decreasing the gain of the terminal
end of each beam. The image data of each beam, for which the gain
adjustment has been performed, is temporarily stored in the buffer
72 for each beam. Then, after image data of the same individual
scan region have been prepared, the alignment unit 74 for each beam
adjusts deviation in the y direction, and the image data of each
beam is output to the averaging unit 76. In the averaging unit 76,
by integrating the image data of the same individual scan region by
the addition unit 77, deviation of the gray scale level at the
connecting portion of each individual scan region after the
integration can be eliminated as shown in FIG. 12. Similarly, in
the subsequent process, when the division unit 78 performs division
by three, an image which has been averaged at the image averaging
frequency being three can be obtained. The averaged image data of
each individual scan region 27 is output to the comparison circuit
108.
[0073] In the comparison step (S130), the comparison circuit 108
compares averaged image data of each individual scan region 27 with
a reference image. Prior to this, the reference image has been
generated.
[0074] In the reference image generation step, the reference image
generation circuit 112 generates a reference image for each
rectangular region 33, based on design data serving as a basis of a
plurality of figure patterns formed on the substrate 101.
Specifically, it operates as follows: First, design pattern data is
read from the storage device 109 through the control computer 110,
and each figure pattern defined in the read design pattern data is
converted into image data of binary or multiple values.
[0075] Basics of figures defined by the design pattern data are,
for example, rectangles and triangles. For example, there is stored
figure data defining the shape, size, position, and the like of
each pattern figure by using information, such as coordinates (x,
y) of the reference position of the figure, lengths of sides of the
figure, and a figure code serving as an identifier for identifying
the figure type such as a rectangle, a triangle and the like.
[0076] When design pattern data serving as the figure data is input
to the reference image generation circuit 112, the data is
developed into data of each figure. Then, the figure code, the
figure dimensions, and the like indicating the figure shape of each
figure data are interpreted. Then, the reference image generation
circuit 112 develops each figure data to design pattern image data
of binary or multiple values as a pattern to be arranged in a
square in units of grids of predetermined quantization dimensions,
and outputs the developed data. In other words, the reference image
generation circuit 112 reads design data, calculates the occupancy
of a figure in the design pattern, for each square region obtained
by virtually dividing the inspection region into squares in units
of predetermined dimensions, and outputs n-bit occupancy data. For
example, it is preferable to set one square as one pixel. Assuming
that one pixel has a resolution of 1/2.sup.8(= 1/256), the
occupancy in each pixel is calculated by allocating small regions
which correspond to the region of figures arranged in the pixel
concerned and each of which corresponds to 1/256 resolution. Then,
the occupancy is generated as 8-bit occupancy data. The square
region (inspection pixel) can be in accordance with the pixel of
measured data.
[0077] Next, the reference image generation circuit 112 performs
filtering processing on design image data of a design pattern which
is image data of a figure, using a predetermined filter function.
Thereby, it is possible to match/fit the design image data being
image data on the design side, whose image intensity (gray scale
level) is represented by digital values, with image generation
characteristics obtained by irradiation with the multiple primary
electron beams 20. The generated image data for each pixel of a
reference image is output to the comparison circuit 108.
[0078] FIG. 13 shows an example of an internal configuration of a
comparison circuit according to the first embodiment. In FIG. 13,
storage devices 52 and 56, such as magnetic disk drives, an
alignment unit 57, and a comparison unit 58 are arranged in the
comparison circuit 108. Each of the "units" such as the alignment
unit 57 and the comparison unit 58 includes processing circuitry.
As the processing circuitry, for example, an electric circuit,
computer, processor, circuit board, quantum circuit, semiconductor
device, or the like can be used. Moreover, each of the "units" may
use common processing circuitry (the same processing circuitry), or
different processing circuitry (separate processing circuitry).
Input data needed in the alignment unit 57 and the comparison unit
58, and calculated results are stored in a memory (not shown) or in
the memory 118 each time.
[0079] According to the first embodiment, the stripe region 32 is
further divided into a plurality of rectangular (including square)
frame regions. The frame region is used as a unit region of an
image to be inspected. In order to prevent missing an image, it is
preferable that the margin region of each frame region overlaps
each other. Also, it is preferable that each of the size in the x
direction and that in the y direction of the frame region is set to
be around an integer fraction (e.g., about 1/2) of the beam pitch
of the multiple primary electron beams 20 on the substrate 101 when
the arrangement of the multiple primary electron beams 20 is in the
x and y directions, without being rotated to be oblique, for
example.
[0080] In the comparison circuit 108, transmitted secondary
electron image data is temporarily stored in the storage device 56,
as a secondary electron image (inspection image to be inspected,
frame image) of each frame region. Similarly, transmitted reference
image data is temporarily stored in the storage device 52, as a
reference image for each frame region.
[0081] In the alignment step, the alignment unit 57 reads, for each
frame region, a frame image serving as an inspection image, and a
reference image corresponding to the frame image, and provides
alignment between both the images, based on units of sub-pixels
smaller than units of pixels. For example, the alignment can be
performed by a least-square method.
[0082] In the comparison step, the comparison unit 58 compares the
frame image (secondary electron image) and the reference image. In
other words, the comparison unit 58 compares, for each pixel,
reference image data with frame image data. The comparison unit 58
compares them, for each pixel, based on predetermined determination
conditions in order to determine whether there is a defect such as
a shape defect. For example, if a gray scale level difference in
each pixel is larger than a determination threshold Th, it is
determined that there is a defect. Then, the comparison result is
output. It may be output specifically to the storage device 109,
the monitor 117, or the memory 118, or alternatively, output from
the printer 119.
[0083] In the examples described above, the die-to-database
inspection is performed. However, it is not limited thereto. The
die-to-die inspection may be conducted. Now, the case of performing
the die-to-die inspection will be described.
[0084] In the alignment step, the alignment unit 57 reads a frame
image (image to be inspected) of the die 1 and a frame image (image
to be inspected) of the die 2 on which the same pattern as that of
the die 1 is formed, and provides alignment between both the
images, based on units of sub-pixels smaller than units of pixels.
For example, the alignment can be performed using a least-squares
method.
[0085] In the comparison step, the comparison unit 58 compares the
frame image of the die 1 with the frame image of the die 2. The
comparison unit 58 compares them, for each pixel, based on
predetermined determination conditions in order to determine
whether there is a defect such as a shape defect. For example, if a
gray scale level difference in each pixel is larger than the
determination threshold Th, it is determined that there is a
defect. Then, the comparison result is output. It is output
specifically to the storage device 109, the monitor 117, or the
memory 118.
[0086] As described above, according to the first embodiment, when
acquiring an image with multiple beams, noise can be reduced based
on averaging processing corresponding to a necessary averaging
frequency, without repeatedly scanning the same position the number
of times needed as the averaging frequency. Therefore, since a
measured image in which noise has been reduced is used, inspection
can be performed with high accuracy.
Second Embodiment
[0087] Although, in the first embodiment, the individual scan
regions 27 extending in the longitudinal direction of the stripe
region 32 are set for each stripe region 32 such that each beam
does not overlap each other in a scanning direction (moving
direction of the stage), and scanning is continuously performed for
each individual scan region 27, it is not limited thereto. A second
embodiment describes the case where, for example, a rectangular
individual block is set and scanned by each beam. The configuration
of the pattern inspection apparatus in the second embodiment is the
same as that of FIG. 1. Moreover, the flowchart of main steps of
the pattern inspection method in the second embodiment is the same
as that of FIG. 7. The contents of the second embodiment are the
same as those of the first embodiment except what is particularly
described below.
[0088] FIGS. 14A and 14B illustrate scanning operations with
multiple beams according to the second embodiment. FIG. 14A shows
the case of the multiple primary electron beams 20 of 3.times.3
(rows by columns). As shown in FIG. 14B, the angle of the moving
direction of the stage 105 and the angle of the arranging direction
of the multiple primary electron beams 20 are relatively shifted
from each other so that a plurality of the primary electron beams
10 of the multiple primary electron beams 20 may not be arranged in
parallel to the moving direction of the stage 105. In the case of
FIG. 14B, by rotating the arranging direction of the multiple
primary electron beams 20 of 3.times.3 on the substrate 101 by, for
example, the tilt angle .theta. shown in the equation (1), a
plurality of the primary electron beams 10 of the multiple primary
electron beams 20 can be arranged not to be parallel to the moving
direction of the stage 105.
[0089] In the parameter setting step (S102), the averaging
frequency setting unit 60 sets, as one of parameters, an image
averaging frequency (that is, the frequency (the number of times)
used for image averaging). The image averaging frequency (the
number of times) can be variably set from one to the number of
beams of the multiple primary electron beams 20. However, in the
case of the image averaging frequency being one, since it does not
change from the original image, it cannot be said that this state
has been averaged. Therefore, here, it is variably set from two to
the number of beams of the multiple primary electron beams. For
example, if the multiple primary electron beams 20 of 3.times.3 can
be applied, the image averaging frequency can be variably set from
two to nine. Moreover, the line scan direction setting unit 61
sets, as another parameter, the line scan direction of each beam.
Here, as shown in FIG. 14A, the line scan direction of each beam is
set to be the direction shifted (rotated) by the tilt angle .theta.
from the y axis, for example.
[0090] In the individual region setting step (S104), the individual
region setting unit 62 sets an individual block region 28 for each
beam as another example of the individual scan region of each beam
on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. According to the second embodiment, a rectangular including
square block scan region whose side has a length of a beam pitch,
being a pitch between mutually adjacent beams, is set for each beam
of the multiple primary electron beams 20. In the example of FIG.
14A, for each beam of the multiple primary electron beams 20, a
region surrounded by a beam pitch in the direction rotated by the
angle .theta. from the x axis and a beam pitch in the direction
rotated by the angle .theta. from the y axis, where the beam
currently concerned is located, is set as the individual block
region 28. In the case of FIG. 14A, there are set nine rectangular
(an example of a quadrangle) including square individual block
regions 28 (individual scan regions) of from 1 to 9, three rows by
three columns, each of which is a region surrounded by the beam
pitch in the direction rotated by the angle .theta. from the x axis
and the beam pitch in the direction rotated by the angle .theta.
from the y axis. In the second embodiment, in FIG. 14A, beams
individually corresponding to the nine individual block regions 28
from 1 to 9 are defined as beams 1 to 9.
[0091] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual block regions
28 of other beams may be included in the direction rotated by the
angle .theta. from the moving direction (the x direction) of the
stage 105 and/or the direction rotated by the angle .theta. from
the y axis which is perpendicular to the moving direction of the
stage 105. In the second embodiment, the scan region width of each
primary electron beam 10 can be set such that the block scan
regions of other beams are included in the two-dimensional
direction. The scan width setting unit 64 variably sets the scan
region width, which is to be scanned by each primary electron beam
10 of the multiple primary electron beams 20 and is in the
direction rotated by the angle .theta. from the x axis and/or the
direction rotated by the angle .theta. from the y axis,
correspondingly depending on the image averaging frequency
(frequency used for image averaging) which can be set variably. In
other words, the scan width setting unit 64 expands the scan region
width of each primary electron beam 10, which is in the direction
rotated by the angle .theta. from the x axis and/or the direction
rotated by the angle .theta. from the y axis, depending on
(corresponding to) the image averaging frequency. As shown in FIG.
14B, the maximum scan region per beam is the nine individual block
regions 28 of 3.times.3 where the individual block region 28 of the
beam currently concerned is located at the lower left corner. For
example, when the image averaging frequency is three, the scan
region width to be scanned by each primary electron beam 10 may be
three individual block regions 28 in the direction rotated by the
angle .theta. from the x axis, or may be three individual block
regions 28 in the direction rotated by the angle .theta. from the y
axis. For example, the scan region to be scanned by the beam 1 may
be individual block regions 28 of the beams 1, 2, and 3, or may be
individual block regions 28 of the beams 1, 4, and 7.
[0092] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105. In the example of FIG. 14B, after each beam scans its
currently associated individual block region 28, the image
acquisition mechanism 150 shifts an irradiation position of each
beam by the distance obtained by dividing the product of the number
of beams and the beam pitch, which are in the direction rotated by
the angle .theta. from the x axis, by sin(.theta.), and then, scans
the next individual block region 28 for each beam. Subsequently,
this is repeated. In the case of FIG. 14B, for example, when the
image averaging frequency is three, the beam 1 scans the three
individual block regions 28 of the beams 1, 4, and 7, for example.
In the case of FIG. 14B, scanning of the individual scan region of
each beam is repeated at a constant pitch. By this, it becomes
possible to acquire an image which is not overlapped except for the
overlapped portion set in the scan width setting step (S106). Then,
by expanding the scan width of each beam in the scan width setting
step (S106), images of the same position can be acquired by a
plurality of beams corresponding to the image averaging
frequency.
[0093] The contents of the subsequent steps are the same as those
of the first embodiment. For example, in the averaging step (S122),
using image data of each beam, the averaging unit 76 in the image
correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set.
[0094] As described above, according to the second embodiment,
similarly to the first embodiment, when acquiring an image with
multiple beams, noise can be reduced based on averaging processing
corresponding to a necessary averaging frequency, without
repeatedly scanning the same position the number of times needed as
the averaging frequency. Therefore, since a measured image in which
noise has been reduced is used, inspection can be performed with
high accuracy.
[0095] Further, according to the second embodiment, when expanding
the scan width in the direction rotated by the angle from the x
axis, it is possible to reduce the influence of difference due to
deviation of gray-scale level values at the beam connecting portion
(image boundary) between individual scan regions 27 which are
mutually adjacent in the direction rotated by the angle .theta.
from the x axis. Moreover, when expanding the scan width in the
direction rotated by the angle .theta. from the y axis, it is
possible to reduce the influence of difference due to deviation of
gray-scale level values at the beam connecting portion (image
boundary) between individual scan regions 27 which are mutually
adjacent in the direction rotated by the angle .theta. from the y
axis. Furthermore, when expanding the scan width in both the
direction rotated by the angle .theta. from the x axis and the
direction rotated by the angle .theta. from the y axis, it is
possible to reduce the influence of difference due to deviation of
gray-scale level values at the beam connecting portions (image
boundaries) between individual scan regions 27 which are mutually
adjacent in both the direction rotated by the angle .theta. from
the x axis and the direction rotated by the angle .theta. from the
y axis.
Third Embodiment
[0096] A third embodiment describes a modified example of the
second embodiment. The configuration of the pattern inspection
apparatus in the third embodiment is the same as that of FIG. 1.
Moreover, the flowchart of main steps of the pattern inspection
method in the third embodiment is the same as that of FIG. 7. The
contents of the third embodiment are the same as those of the first
or second embodiment except what is particularly described
below.
[0097] FIGS. 15A and 15B illustrate scanning operations with
multiple beams according to the third embodiment. FIG. 15A shows
the case of the multiple primary electron beams 20 of 3.times.3
(rows by columns). As shown in FIG. 15B, the angle of the moving
direction of the stage 105 and the angle of the arranging direction
of the multiple primary electron beams 20 are relatively shifted
from each other so that a plurality of the primary electron beams
10 of the multiple primary electron beams 20 may not be arranged in
parallel to the moving direction of the stage 105. In the case of
FIG. 15B, by rotating the arranging direction of the multiple
primary electron beams 20 of 3.times.3 on the substrate 101 by, for
example, the tilt angle .theta. shown in the equation (1), a
plurality of the primary electron beams 10 of the multiple primary
electron beams 20 can be arranged not to be parallel to the moving
direction of the stage 105.
[0098] The contents of the parameter setting step (S102) are the
same as those of the second embodiment. The line scan direction
setting unit 61 sets, as another parameter, the line scan direction
of each beam. Here, as shown in FIG. 15A, the line scan direction
of each beam is set to be the direction shifted (rotated) by the
tilt angle .theta. from the y axis, for example.
[0099] In the individual region setting step (S104), the individual
region setting unit 62 sets the individual block region 28 for each
beam as another example of the individual scan region of each beam
on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. In the case of FIG. 15A, for each beam of the multiple
primary electron beams 20, the individual region setting unit 62
sets, as the individual block region 28, a parallelogram (an
example of a quadrangle) region having a side length obtained by
dividing the beam pitch in the direction rotated by the angle
.theta. from the x axis by sin (.theta.) and another side length of
the beam pitch in the direction rotated by the angle .theta. from
the y axis. In the example of FIG. 15A, for each beam, the
individual region setting unit 62 sets nine quadrangular individual
block regions 28 (individual scan regions) of from 1 to 9, three
rows by three columns, each of which is a parallelogram region
having a side length obtained by dividing the beam pitch in the
direction rotated by the angle .theta. from the x axis by sin
(.theta.) and another side length of the beam pitch in the
direction rotated by the angle .theta. from the y axis.
[0100] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual block regions
28 of other beams may be included in the direction of the moving
direction (the x direction) of the stage 105 and/or the direction
rotated by the angle .theta. from the y axis which is perpendicular
to the moving direction of the stage 105. The scan width setting
unit 64 variably sets the scan region width, which is to be scanned
by each primary electron beam 10 of the multiple primary electron
beams 20 and is in the x direction and/or the direction rotated by
the angle .theta. from the y axis, correspondingly depending on the
image averaging frequency (frequency used for image averaging)
which can be set variably. In other words, the scan width setting
unit 64 expands the scan region width of each primary electron beam
10, in the x direction and/or the direction rotated by the angle
.theta. from the y axis, correspondingly depending on the image
averaging frequency. As shown in FIG. 15B, the maximum scan region
per beam is the region surrounded by the width of three individual
block regions 28 in the x direction and the width of three
individual block regions 28 in the direction rotated by the angle
.theta. from the y axis, where the individual block region 28 of
the beam currently concerned is located at the lower left
corner.
[0101] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105. In the example of FIG. 15B, after each beam scans its
currently associated individual block region 28, the image
acquisition mechanism 150 shifts the irradiation position of each
beam by the distance obtained by dividing the product of the number
of beams and the beam pitch, which are in the direction rotated by
the angle .theta. from the x axis, by sin(.theta.), and then, scans
the next individual block region 28 for each beam. Subsequently,
this is repeated. In the example of FIG. 15B, for example, in the
case of the image averaging frequency being three and expanding the
scan region width in the direction rotated by the angle .theta.
from the y axis, the beam 3 scans the three individual block
regions 28 of the beams 3, 6, and 9, for example. On the other
hand, in the case of expanding the scan region width in the x
direction, for example, the beam 3 scans the individual block
region 28 of the beam 3, a part of the individual block region 28
of the beam 1, a part of the individual block region 28 of the beam
4, apart of the individual block region 28 of the beam 2, and a
part of the individual block region 28 of the beam 5. Thus, the
boundaries of the individual block regions 28 arranged in the x
direction can be shifted.
[0102] In the example of FIG. 15B, scanning of the individual scan
region of each beam is repeated at a constant pitch. By this, it
becomes possible to acquire an image which is not overlapped except
for the overlapped portion set in the scan width setting step
(S106). Then, by expanding the scan width of each beam in the scan
width setting step (S106), images of the same position can be
acquired by a plurality of beams corresponding to the image
averaging frequency.
[0103] The contents of the subsequent steps are the same as those
of the first embodiment. For example, in the averaging step (S122),
using image data of each beam, the averaging unit 76 in the image
correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set.
[0104] As described above, according to the third embodiment,
similarly to the first and second embodiments, when acquiring an
image with multiple beams, noise can be reduced based on averaging
processing corresponding to a necessary averaging frequency,
without repeatedly scanning the same position the number of times
needed as the averaging frequency. Therefore, since a measured
image in which noise has been reduced is used, inspection can be
performed with high accuracy.
[0105] Moreover, according to the third embodiment, since
boundaries in the y direction of the individual block regions 28
arranged in the x direction shift, when expanding the scan width in
the x direction, it is possible to reduce the influence of
difference due to deviation of gray-scale level values at the beam
connecting portion (image boundary) between individual scan regions
27 which are mutually adjacent in the x direction and the direction
rotated by the angle .theta. from the y axis.
Fourth Embodiment
[0106] A fourth embodiment describes a modified example of the
third embodiment. The configuration of the pattern inspection
apparatus in the fourth embodiment is the same as that of FIG. 1.
Moreover, the flowchart of main steps of the pattern inspection
method in the fourth embodiment is the same as that of FIG. 7. The
contents of the fourth embodiment are the same as those of any of
the first to third embodiments except what is particularly
described below.
[0107] FIGS. 16A and 16B illustrate scanning operations with
multiple beams according to the fourth embodiment. FIG. 16A shows
the case of the multiple primary electron beams 20 of 3.times.3
(rows by columns). As shown in FIG. 16B, the angle of the moving
direction of the stage 105 and the angle of the arranging direction
of the multiple primary electron beams 20 are relatively shifted
from each other so that a plurality of the primary electron beams
10 of the multiple primary electron beams 20 may not be arranged in
parallel to the moving direction of the stage 105. In the case of
FIG. 16B, by rotating the arranging direction of the multiple
primary electron beams 20 of 3.times.3 on the substrate 101 by, for
example, the tilt angle .theta. shown in the equation (1), a
plurality of the primary electron beams 10 of the multiple primary
electron beams 20 can be arranged not to be parallel to the moving
direction of the stage 105.
[0108] The contents of the parameter setting step (S102) are the
same as those of the second embodiment. The line scan direction
setting unit 61 sets, as another parameter, the line scan direction
of each beam. Here, as shown in FIG. 16A, the line scan direction
of each beam is set to be the direction shifted (rotated) by the
tilt angle .theta. from the y axis, for example.
[0109] In the individual region setting step (S104), the individual
region setting unit 62 sets the individual block region 28 for each
beam as another example of the individual scan region of each beam
on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. In the case of FIG. 16A, for each beam of the multiple
primary electron beams 20, the individual region setting unit 62
sets, as the individual block region 28, a parallelogram region
having a side length of half of what is obtained by dividing the
beam pitch in the direction rotated by the angle .theta. from the x
axis by sin(8) and another side length of the beam pitch in the
direction rotated by the angle .theta. from the y axis. The example
of FIG. 16A shows the state where an example of the individual
block region 28 of FIG. 15A is divided into two in the x direction.
In the case of FIG. 16A, for each beam, the individual region
setting unit 62 sets nine quadrangular individual block regions 28
(individual scan regions) of from 1 to 9, three rows by three
columns, each of which is a parallelogram region having a side
length of half of what is obtained by dividing the beam pitch in
the direction rotated by the angle .theta. from the x axis by
sin(.theta.) and another side length of the beam pitch in the
direction rotated by the angle .theta. from the y axis.
[0110] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual block regions
28 of other beams may be included in the direction of the moving
direction (the x direction) of the stage 105 and/or the direction
rotated by the angle .theta. from the y axis which is perpendicular
to the moving direction of the stage 105. The scan width setting
unit 64 variably sets the scan region width, which is to be scanned
by each primary electron beam 10 of the multiple primary electron
beams 20 and is in the x direction and/or the direction rotated by
the angle .theta. from the y axis, correspondingly depending on the
image averaging frequency (frequency used for image averaging)
which can be set variably. In other words, the scan width setting
unit 64 expands the scan region width of each primary electron beam
10, in the x direction and/or the direction rotated by the angle
.theta. from the y axis, correspondingly depending on the image
averaging frequency. As shown in FIG. 16B, the maximum scan region
per beam is the region surrounded by the width of three individual
block regions 28 in the x direction and the width of three
individual block regions 28 in the direction rotated by the angle
.theta. from the y axis, where the individual block region 28 of
the beam currently concerned is located at the lower left
corner.
[0111] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105. In the example of FIG. 16B, after each beam scans its
currently associated individual block region 28, the image
acquisition mechanism 150 shifts the irradiation position of each
beam by the distance obtained by dividing the product of the number
of beams and 1/2 of the beam pitch, which are in the direction
rotated by the angle .theta. from the x axis, by sin(.theta.), and
then, scans the next individual block region 28 for each beam.
Subsequently, this is repeated. In the example of FIG. 16B, for
example, in the case of the image averaging frequency being three
and expanding the scan region width in the direction rotated by the
angle .theta. from the y axis, the beam 3 scans the three
individual block regions 28 of the beams 3, 6, and 9, for example.
On the other hand, in the case of expanding the scan region width
in the x direction, for example, the beam 3 scans the individual
block region 28 of the beam 3, a part of the individual block
region 28 of the beam 2, a part of the individual block region 28
of the beam 5, a part of the individual block region 28 of the beam
1, and a part of the individual block region 28 of the beam 4.
Thus, the boundaries of the individual block regions 28 arranged in
the x direction can be shifted.
[0112] In the example of FIG. 16B, scanning of the individual scan
region of each beam is repeated at a constant pitch. According to
the fourth embodiment, even when the individual block region 28 in
the stage moving direction is divided, an image can be acquired
without a space. Thus, it becomes possible to acquire an image
which is not overlapped except for the overlapped portion set in
the scan width setting step (S106). Then, by expanding the scan
width of each beam in the scan width setting step (S106), images of
the same position can be acquired by a plurality of beams
corresponding to the image averaging frequency.
[0113] The contents of the subsequent steps are the same as those
of the first embodiment. For example, in the averaging step (S122),
using image data of each beam, the averaging unit 76 in the image
correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set.
[0114] As described above, according to the fourth embodiment,
similarly to the first, second, and third embodiments, when
acquiring an image with multiple beams, noise can be reduced based
on averaging processing corresponding to a necessary averaging
frequency, without repeatedly scanning the same position the number
of times needed as the averaging frequency. Therefore, since a
measured image in which noise has been reduced is used, inspection
can be performed with high accuracy.
[0115] Moreover, similarly to the third embodiment, since
boundaries in the y direction of the individual block regions 28
arranged in the x direction shift, when expanding the scan width in
the x direction, it is possible to reduce the influence of
difference due to deviation of gray-scale level values at the beam
connecting portion (image boundary) between individual scan regions
27 which are mutually adjacent in the x direction and the direction
rotated by the angle .theta. from the y axis. Further, according to
the fourth embodiment, since the size of the individual block
region 28 in the x direction can be decreased, it is possible to
reduce the deflection width in the x direction of the multiple
primary electron beams 20.
Fifth Embodiment
[0116] A fifth embodiment describes a modified example of the
fourth embodiment. The configuration of the pattern inspection
apparatus in the fifth embodiment is the same as that of FIG. 1.
Moreover, the flowchart of main steps of the pattern inspection
method in the fifth embodiment is the same as that of FIG. 7. The
contents of the fifth embodiment are the same as those of any of
the first to fourth embodiments except what is particularly
described below.
[0117] FIGS. 17A and 17B illustrate scanning operations with
multiple beams according to the fifth embodiment. FIG. 17A shows
the case of the multiple primary electron beams 20 of 3.times.3
(rows by columns). As shown in FIG. 17B, the angle of the moving
direction of the stage 105 and the angle of the arranging direction
of the multiple primary electron beams 20 are relatively shifted
from each other so that a plurality of the primary electron beams
10 of the multiple primary electron beams 20 may not be arranged in
parallel to the moving direction of the stage 105. In the case of
FIG. 17B, by rotating the arranging direction of the multiple
primary electron beams 20 of 3.times.3 on the substrate 101 by, for
example, the tilt angle .theta. shown in the equation (1), a
plurality of the primary electron beams 10 of the multiple primary
electron beams 20 can be arranged not to be parallel to the moving
direction of the stage 105.
[0118] The contents of the parameter setting step (S102) are the
same as those of the second embodiment. The line scan direction
setting unit 61 sets, as another parameter, the line scan direction
of each beam. Here, as shown in FIG. 17A, the line scan direction
of each beam is set to be, for example, the y direction without
shifting by the tilt angle .theta..
[0119] In the individual region setting step (S104), the individual
region setting unit 62 sets the individual block region 28 for each
beam as another example of the individual scan region of each beam
on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. In the case of FIG. 17A, for each beam of the multiple
primary electron beams 20, the individual region setting unit 62
sets, as the individual block region 28, a rectangular region
having a side length of half of what is obtained by dividing the
beam pitch in the direction rotated by the angle .theta. from the x
axis by sin(.theta.) and another side length of the beam pitch in
the y direction. In the case of FIG. 17A, for each beam, the
individual region setting unit 62 sets nine rectangular individual
block regions 28 (individual scan regions) of from 1 to 9, three
rows by three columns, each of which is a rectangular region having
a side length of half of what is obtained by dividing the beam
pitch in the direction rotated by the angle .theta. from the x axis
by sin(.theta.) and another side length of the beam pitch in the y
direction.
[0120] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual block regions
28 of other beams may be included in the direction of the moving
direction (the x direction) of the stage 105 and/or the y direction
perpendicular to the moving direction of the stage 105. The scan
width setting unit 64 variably sets the scan region width, which is
to be scanned by each primary electron beam 10 of the multiple
primary electron beams 20 and is in the x direction and/or the y
direction, correspondingly depending on the image averaging
frequency (frequency used for image averaging) which can be set
variably. In other words, the scan width setting unit 64 expands
the scan region width of each primary electron beam 10, in the x
direction and/or the y direction, correspondingly depending on the
image averaging frequency. As shown in FIG. 17B, the maximum scan
region per beam is the region surrounded by the width of three
individual block regions 28 in the x direction and the width of
three individual block regions 28 in the y direction, where the
individual block region 28 of the beam currently concerned is
located at the lower left corner.
[0121] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105. In the example of FIG. 17B, after each beam scans its
currently associated individual block region 28, the image
acquisition mechanism 150 shifts the irradiation position of each
beam by the distance obtained by dividing the product of the number
of beams and 1/2 of the beam pitch, which are in the direction
rotated by the angle .theta. from the x axis, by sin(.theta.), and
then, scans the next individual block region 28 for each beam.
Subsequently, this is repeated. In the example of FIG. 17B, for
example, in the case of the image averaging frequency being three
and expanding the scan region width in the y direction, the beam 3
scans the three individual block regions 28 of the beams 3, 6, and
9, for example. On the other hand, in the case of expanding the
scan region width in the x direction, for example, the beam 3 scans
the individual block region 28 of the beam 3, a part of the
individual block region 28 of the beam 2, a part of the individual
block region 28 of the beam 5, a part of the individual block
region 28 of the beam 1, and a part of the individual block region
28 of the beam 4. Thus, the boundaries of the individual block
regions 28 arranged in the x direction can be shifted.
[0122] In the example of FIG. 17B, scanning of the individual scan
region of each beam is repeated at a constant pitch. According to
the fifth embodiment, without inclining the individual block region
28, when the beam arrangement is inclined against the stage moving
direction, an image can be acquired without a space. In other
words, 90 degree scanning can be performed against the x axis.
Thereby, it becomes possible to acquire an image which is not
overlapped except for the overlapped portion set in the scan width
setting step (S106). Then, by expanding the scan width of each beam
in the scan width setting step (S106), images of the same position
can be acquired by a plurality of beams corresponding to the image
averaging frequency.
[0123] The contents of the subsequent steps are the same as those
of the first embodiment. For example, in the averaging step (S122),
using image data of each beam, the averaging unit 76 in the image
correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set.
[0124] As described above, according to the fifth embodiment,
similarly to the first to fourth embodiments, when acquiring an
image with multiple beams, noise can be reduced based on averaging
processing corresponding to a necessary averaging frequency,
without repeatedly scanning the same position the number of times
needed as the averaging frequency. Therefore, since a measured
image in which noise has been reduced is used, inspection can be
performed with high accuracy.
[0125] Moreover, similarly to the third and fourth embodiments,
since boundaries in the y direction of the individual block regions
28 arranged in the x direction shift, when expanding the scan width
in the x direction, it is possible to reduce the influence of
difference due to deviation of gray-scale level values at the beam
connecting portion (image boundary) between individual scan regions
27 which are mutually adjacent in the x direction and the direction
rotated by the angle .theta. from the y axis. Further, according to
the fifth embodiment, since the size of the individual block region
28 in the x direction can be decreased, it is possible to reduce
the deflection width in the x direction of the multiple primary
electron beams 20.
Sixth Embodiment
[0126] A sixth embodiment describes a modified example of the first
embodiment. The configuration of the pattern inspection apparatus
in the sixth embodiment is the same as that of FIG. 1. Moreover,
the flowchart of main steps of the pattern inspection method in the
sixth embodiment is the same as that of FIG. 7. The contents of the
sixth embodiment are the same as those of any of the first to
fourth embodiments except what is particularly described below.
[0127] FIG. 18 illustrates scanning operations with multiple beams
according to the sixth embodiment. FIG. 18 shows the case of the
multiple primary electron beams 20 of 3.times.3 (rows by columns).
As shown in FIG. 18, the angle of the moving direction of the stage
105 and the angle of the arranging direction of the multiple
primary electron beams 20 are relatively shifted from each other so
that a plurality of the primary electron beams 10 of the multiple
primary electron beams 20 may not be arranged in parallel to the
moving direction of the stage 105. In the case of FIG. 18, by
rotating the arranging direction of the multiple primary electron
beams 20 of 3.times.3 on the substrate 101 by, for example, the
tilt angle .theta. shown in the equation (1), a plurality of the
primary electron beams 10 of the multiple primary electron beams 20
can be arranged not to be parallel to the moving direction of the
stage 105.
[0128] The contents of the parameter setting step (S102) are the
same as those of the second embodiment. The line scan direction
setting unit 61 sets, as another parameter, the line scan direction
of each beam. Here, as shown in FIG. 18, the line scan direction of
each beam is set to be, for example, the y direction without
shifting by the tilt angle .theta..
[0129] In the individual region setting step (S104), the individual
region setting unit 62 sets the individual block region 28 for each
beam as another example of the individual scan region of each beam
on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. In the case of FIG. 18, for each beam of the multiple
primary electron beams 20, the individual region setting unit 62
divides each individual scan region 27 extending in the x direction
shown in FIG. 4B into a plurality of individual block regions 28 by
the size obtained by dividing the product of the number of beams
and the beam pitch, which are in the direction rotated by the angle
.theta. from the x axis, by sin (.theta.). Moreover, the individual
block region 28 adjacent in the y direction is set to be shifted by
the size obtained by dividing by sin(.theta.) the beam pitch in the
direction rotated by the angle .theta. from the x axis.
[0130] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual block regions
28 of other beams may be included in the y direction perpendicular
to the moving direction of the stage 105. The scan width setting
unit 64 variably sets the scan region width in the y direction
which is to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20, correspondingly depending on
the image averaging frequency which can be set variably. In other
words, the scan width setting unit 64 expands the scan region width
in the y direction of each primary electron beam 10,
correspondingly depending on the image averaging frequency. As
shown in FIG. 18, the maximum scan region per beam is the region of
nine individual block regions 28 in the y direction including the
individual block region 28 of the beam currently concerned.
[0131] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105. In the example of FIG. 18, after each beam scans its currently
associated individual block region 28, the image acquisition
mechanism 150 shifts the irradiation position of each beam by the
distance obtained by dividing the product of the number of beams
and the beam pitch, which are in the direction rotated by the angle
.theta. from the x axis, by sin(.theta.), and then, scans the next
individual block region 28 for each beam. Subsequently, this is
repeated. In the example of FIG. 18, for example, in the case of
the image averaging frequency being three and expanding the scan
region width in the y direction, the beam 3 scans the individual
block region 28 of the beam 3, a part of the individual block
region 28 of the beam 4, and a part of the individual block region
28 of the beam 5. Thus, the boundaries in the x direction of the
individual block regions 28 arranged in the y direction can be
shifted.
[0132] According to the sixth embodiment, the one-dimensional
scanning described in the first embodiment can be carried out as a
repetition of two-dimensional scanning. Thereby, it becomes
possible to acquire an image which is not overlapped except for the
overlapped portion set in the scan width setting step (S106). Then,
by expanding the scan width of each beam in the scan width setting
step (S106), images of the same position can be acquired by a
plurality of beams corresponding to the image averaging
frequency.
[0133] The contents of the subsequent steps are the same as those
of the first embodiment. For example, in the averaging step (S122),
using image data of each beam, the averaging unit 76 in the image
correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set.
[0134] As described above, according to the sixth embodiment,
similarly to the first to fourth embodiments, when acquiring an
image with multiple beams, noise can be reduced based on averaging
processing corresponding to a necessary averaging frequency,
without repeatedly scanning the same position the number of times
needed as the averaging frequency. Therefore, since a measured
image in which noise has been reduced is used, inspection can be
performed with high accuracy.
Seventh Embodiment
[0135] A seventh embodiment describes a modified example of the
third embodiment. The configuration of the pattern inspection
apparatus in the seventh embodiment is the same as that of FIG. 1.
Moreover, the flowchart of main steps of the pattern inspection
method in the seventh embodiment is the same as that of FIG. 7. The
contents of the seventh embodiment are the same as those of any of
the first to fourth embodiments except what is particularly
described below.
[0136] FIGS. 19A and 19B illustrate scanning operations with
multiple beams according to the seventh embodiment. FIGS. 19A and
19B show the case of the multiple primary electron beams 20 of
3.times.3 (rows by columns). In FIGS. 19A and 19B, each arrangement
of beams of 1, 2, and 3, beams of 4, 5, and 6, and beams of 7, 8,
and 9 is in the y direction, where the arrangements are arranged in
the x direction. As shown in FIGS. 19A and 19B, the angle of the
moving direction of the stage 105 and the angle of the arranging
direction of the multiple primary electron beams 20 are relatively
shifted from each other so that a plurality of the primary electron
beams 10 of the multiple primary electron beams 20 may not be
arranged in parallel to the moving direction of the stage 105. In
the case of FIGS. 19A and 19B, by rotating the arranging direction
of the multiple primary electron beams 20 of 3.times.3 on the
substrate 101 by, for example, the tilt angle .theta. shown in the
equation (1), a plurality of the primary electron beams 10 of the
multiple primary electron beams 20 can be arranged not to be
parallel to the moving direction of the stage 105.
[0137] The contents of the parameter setting step (S102) are the
same as those of the second embodiment. The line scan direction
setting unit 61 sets, as another parameter, the line scan direction
of each beam. Here, as shown in FIG. 19A, the line scan direction
of each beam is set to be the direction shifted (rotated) by the
tilt angle .theta. from the y axis, for example.
[0138] In the individual region setting step (S104), the individual
region setting unit 62 sets the individual block region 28 for each
beam as another example of the individual scan region of each beam
on the substrate 101 which extends in parallel to the moving
direction of the stage 105, by relatively shifting the angle of the
moving direction of the stage 105 and the angle of the array
arranging direction of multiple primary electron beams from each
other. In the case of FIG. 19A, for each beam of the multiple
primary electron beams 20, the individual region setting unit 62
sets, as the individual block region 28, a rectangular region
having a side length of half of the beam pitch in the direction
rotated by the angle .theta. from the x axis and another side
length of the beam pitch in the direction rotated by the angle
.theta. from the y axis. The example of FIG. 19A shows the state
where an example of the individual block region 28 of FIG. 14A is
divided into two in the x direction.
[0139] In the scan width setting step (S106), the scan width
setting unit 64 variably sets the scan region width (individual
beam scan width) of each beam so that the individual block regions
28 of other beams may be included in the direction rotated by the
angle .theta. from the moving direction (the x direction) of the
stage 105 and/or the direction rotated by the angle .theta. from
the y axis which is perpendicular to the moving direction of the
stage 105. The scan width setting unit 64 variably sets the scan
region width, which is to be scanned by each primary electron beam
10 of the multiple primary electron beams 20 and is in the
direction rotated by the angle .theta. from the x axis and/or the
direction rotated by the angle .theta. from the y axis,
correspondingly depending on the image averaging frequency
(frequency used for image averaging) which can be set variably. In
other words, the scan width setting unit 64 expands the scan region
width of each primary electron beam 10, which is in the direction
rotated by the angle .theta. from the x axis and/or the direction
rotated by the angle .theta. from the y axis, depending on
(corresponding to) the image averaging frequency. As shown in FIG.
19B, the maximum scan region per beam is the region surrounded by
the width of three individual block regions 28 in the direction
rotated by the angle .theta. from the x axis and the width of three
individual block regions 28 in the direction rotated by the angle
.theta. from the y axis, where the individual block region 28 of
the beam currently concerned is located at the lower left
corner.
[0140] In the scanning step (S108), in the state where the scan
region width to be scanned by each primary electron beam 10 of the
multiple primary electron beams 20 has been variably set
correspondingly depending on the image averaging frequency which
can be set variably, the image acquisition mechanism 150 acquires
image data of each beam by scanning the substrate 101 with the
multiple primary electron beams 20 deflected by the sub deflector
209 while relatively shifting the angle of the moving direction of
the stage 105 and the angle of the arranging direction of the
multiple primary electron beams 20 from each other so that a
plurality of beams of the multiple primary electron beams 20 may
not be arranged in parallel to the moving direction of the stage
105. In the example of FIG. 19B, after each beam scans its
currently associated individual block region 28, the image
acquisition mechanism 150 shifts the irradiation position of each
beam by the distance obtained by dividing the product of the number
of beams and 1/2 of the beam pitch, which are in the direction
rotated by the angle .theta. from the x axis, by sin (.theta.), and
then, scans the next individual block region 28 for each beam.
Subsequently, this is repeated. In the example of FIG. 19B, for
example, in the case of the image averaging frequency being three
and expanding the scan region width in the direction rotated by the
angle .theta. from the y axis, the beam 1 scans the three
individual block regions 28 of the beams 1, 2, and 3, for example.
On the other hand, in the case of expanding the scan region width
in the direction rotated by the angle .theta. from the x axis, for
example, the beam 1 scans the individual block region 28 of the
beam 1, a part of the individual block region 28 of the beam 7, a
part of the individual block region 28 of the beam 9, and a part of
the individual block region 28 of the beam 4. Thus, the boundaries
of the individual block regions 28 arranged in the direction
rotated by the angle .theta. from the x axis can be shifted.
[0141] In the example of FIG. 19B, scanning of the individual scan
region of each beam is repeated at a constant pitch. According to
the seventh embodiment, even when the individual block region 28 in
the stage moving direction is divided, an image can be acquired
without a space. Thus, it becomes possible to acquire an image
which is not overlapped except for the overlapped portion set in
the scan width setting step (S106). Then, by expanding the scan
width of each beam in the scan width setting step (S106), images of
the same position can be acquired by a plurality of beams
corresponding to the image averaging frequency.
[0142] The contents of the subsequent steps are the same as those
of the first embodiment. For example, in the averaging step (S122),
using image data of each beam, the averaging unit 76 in the image
correction circuit 141 averages errors of the image data by
superimposing image data of the same position at the number being
the same as that indicated by an image averaging frequency having
been set.
[0143] As described above, according to the seventh embodiment, in
addition to the effect of the second embodiment, further, it is
possible to reduce the deflection width in the x direction of the
multiple primary electron beams 20 since the size of the individual
block region 28 in the x direction can be decreased.
[0144] In the above description, each " . . . circuit" includes
processing circuitry. As the processing circuitry, for example, an
electric circuit, computer, processor, circuit board, quantum
circuit, semiconductor device, or the like can be used. Each " . .
. circuit" may use common processing circuitry (the same processing
circuitry), or different processing circuitry (separate processing
circuitry). A program for causing a processor to execute processing
or the like may be stored in a recording medium, such as a magnetic
disk drive, magnetic tape drive, FD, ROM (Read Only Memory), etc.
For example, the position circuit 107, the comparison circuit 108,
the reference image generation circuit 112, the stage control
circuit 114, the lens control circuit 124, the blanking control
circuit 126, the deflection control circuit 128, the scan region
setting circuit 140, and the image correction circuit 141 may be
configured by at least one processing circuit described above.
[0145] Embodiments have been explained referring to specific
examples described above. However, the present invention is not
limited to these specific examples. Although FIG. 1 describes the
case where the multiple primary electron beams 20 are formed by the
shaping aperture array substrate 203 irradiated with one beam from
the electron gun 201 serving as an irradiation source, it is not
limited thereto. The multiple primary electron beams 20 may be
formed by individual irradiation with primary electron beams from a
plurality of irradiation sources.
[0146] While the apparatus configuration, control method, and the
like not directly necessary for explaining the present invention
are not described, some or all of them can be appropriately
selected and used on a case-by-case basis when needed.
[0147] In addition, any other multiple electron beam inspection
apparatus and multiple electron beam inspection method that include
elements of the present invention and that can be appropriately
modified by those skilled in the art are included within the scope
of the present invention.
[0148] Additional advantages and modification will readily occur to
those skilled in the art. Therefore, the invention in its broader
aspects is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *